Plant mitochondrial DNA

Abstract

Sitmmary. DNA was isolated from a mitochondrial fraction of each of the following plant materials: Mung bean (Phascolus aureuis) etiolated hypocotyl; turnip (Brassica rapa) root; sweet wtato (Iponioea batatas) root; and onion (Allium cepa) bulb. It was found that all of these nitochondrial fractions contained DNA, the densities of which were identical (p=1.706 gcm3). An additional DNA (p=1.695) band found in the mitochondrial fraction of Birassica rapa, was identical to DNA separately isolated from the chloroplast-rich fraction. The origin of the second DNA from Alliutm mito-chondrial fraction was not identified. Contrary to the identity of the mitochondrial DNA, DNA from nuclear fractions differed not only with each other but fronm the corresponding mitochondrial DNA. DNA from Phaseoluts and Brassica mitochondria showed the hyperchromicity characteristic of double strainded, native DNA upon heating; Tm's in 0.0195 Na+ were the same; 72.00. The amount of DNA within the mitoch!ondrion of Phascolus was estimated to be 5.0 X 1010 ug; this estimate was made by isolating the mitochondrial DNA concomitantly with the known amiount of added 15N2H B. subtilis DNA (p=1.740). Approximately the samiie amount of DNA was presenit in the mitochondrion of Brassica or Ipomoea. The presence of mitochondrial DNA has been postulated from various experimental observations, such as the incorporation of 3H-thymidine (1, 14), Feulegen staining bodies (1) and most extensively, the DNA-like fibrils resolved by the electromicro-scopic studies made with various organisms (8). Early genetic studies obtained with "petite" in yeast (2) and "poky" in Neurospora (see 19), together with the demonstration by Luck (4) that the mitochondrion is an autonomous replicating unit, may be well reconciled with the idea that mitochondria contain DNA which carries essential information necessary for the function and the replication of the mito-chondria. To support this notion, Luck and Reich (5) succeeded not only in isolating DNA from Neu-rospora mitochondria, but also in demonstrating that this DNA possibly serves as a template for RNA synthesis within the mitochonid(rioni. Subsequent studies carried out in our laboratory with Tetrahyinienia and Paramecium confirmed the presence of DNA within mitochondria in these organisms and showed that mitochondrial DNA in these organismiis markedly differ not only from the respective niuclear DNA, but with each other (18). According to the extensive analysis by Sueoka (15, 16) of DNA of various organisms, cellular DNA reflects the phylogenetic relations as the mean base compositions of DNA from related organisms are similar. It 1 This work was supported by grants from the National Science Foundation. was originally hoped that mitochondrial DNA woulcl exhibit such a relationship. The contrary results obtained in protozoa have prompted us to extend this kind of analysis to mitochondria of different organisms. This paper reports that among plant species the DNA of the mitochondria are essentially identical in terms of t...

Utilization of somatic fusion techniques for the development of HLB tolerant breeding resources employing the Australian finger lime (Citrus australasica)

“…In contrast, there is evidence of abundant plastids and plastid genomes in mesophyll protoplasts [ 46 ] and significant populations of replicating plastid and mitochondrial DNA molecules in suspension-cultured plant cells [ 47 – 50 ]. Because of the complex organization and active recombination of plant mitochondrial genomes [ 51 , 52 ], some contribution of the ‘Page’ mandarin mitochondrial genome sequences to the somatic hybrids and cybrids cannot be ruled out.…”

Plant Organellar DNA Polymerases Evolved Multifunctionality through the Acquisition of Novel Amino Acid Insertions

“…The moderate and low nucleotide incorporation fidelity by AtPOLIA and AtPOLIB is puzzlingly, especially because mitochondrial and plastid genomes in flowering plants present some of the slowest substitution rates in nature [41,42]. Plant genomes harbor enzymatic components like RECA or RADA, that by homologous recombination may ameliorate the misincorporation events generated by AtPOLIs [25,26,43]. However, the enzymatic mechanisms that propitiate a low substitution rate in plant organelles are unknown.…”

“…Although plant organellar DNA polymerases and animal mitochondrial DNA polymerases are distantly related, other components of the replication and transcription apparatus in plant and animal mitochondria like RNA polymerases, primase-helicases, and single-stranded binding proteins share sequence and structural homology with proteins from T-odd bacteriophages [6,[23][24][25][26][27][28][29]. As POPs are the only DNAPs found in plant organelles, they are predicted to be essential for plant organellar DNA replication, and the impossibility to make double AtPOLI mutants indicates that at least one AtPOLI paralog is indispensable for cellular viability [15,16].…”

Plant Organelle Genome Replication

“…In contrast to animals, plant mtDNA contains many more genes and large portions of non-coding or undefined DNA [41]. A typical plant mitochondrial genome encodes anywhere between 50 and 100 genes [42]. The large genome size is at least partially due to the presence of non-coding DNA sequences, which consist of introns, repeats, and duplications of regions of the genome [41,43].…”